It is known that small gas engines are used on equipment and vehicles such as lawn mowers, lawn tractors, and the like. When used on lawn mowers, for example, the engines are exposed to the environment where they may be subject to debris, dirt, moisture, or other contaminants. To maintain the proper functioning of the gas engine, air filters are used to screen and filter the air that is taken in by the engine and more specifically the carburetor of the engine. In many applications, the air filter is concealed from view and therefore when dirt or debris is on the filter, thereby restricting the air flow, this condition is not readily apparent to the operator.
To overcome this problem, known engines sometimes include a sensor mechanism to detect if the dirt or debris on the air filter is restricting the air flow to the engine. As the air filter on the engine becomes dirty and the air flow becomes restricted, vacuum is increased in the air intake line of the engine downstream from the air filter. Conventionally, the vacuum created by the air restriction is detected by a spring-loaded sensor device, a micro-switch, or both, that show the operator the state of the air filter restriction. The springs or micro-switches, however, wear out over time, can give false readings from the engine vibration, or can be difficult to calibrate.
The present invention is directed at improving upon known air filter restriction sensor assemblies and in particular air filter restriction sensor assemblies for small gas engines.